Electrical control system



Jan. 20, l1942. F, Q KEAR 2,270,308

ELECTRICAL CONTROL SYSTEM Filed Nov. 1, 1935 [29.2. ,DA/24am w/Aaf .f5 'i l OAD Patented Jan. 20, 1942 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 13 Claims.

The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment of any royalty thereon.

My invention relates, generally, to methods and apparatus for maintaining constant phase and amplitude relations of voltage and current in electrical loads of which the parameters may vary and which may be energized from a common source of power, and more particularly relates to radio beacon systems in which there is a plurality of directive antennas energized from a common source of high frequency alternating current.

For example: It has been found that in radio beacon systems of the type using a plurality of spaced antennas, the space pattern of the beacon is altered by changes in the constants of one or more of the antennas. These changes are caused by the erratic shifts in weather .conditions surrounding the antenna and by various changes in the locality of one of the antenna of the radio beacon group.

I have found that for an array of antennas to maintain its space pattern without distortion it is necessary that the currents in the various elements of the array remain fixed as to relative phase and magnitude, regardless of changes in the circuit constants. One object of my invention is to provide methods and means for maintaining constant phase and amplitude relationships between voltages and/or currents in interconnected circuit elements. Another object of my` invention is the maintaining of a constant space pattern of a directive radio beacon by maintaining constant phase and amplitude relationship between voltages and/or currents in the antennas and interconnecting networks of the radio beacon. Other objects of my invention will become apparent as the description thereof as applied to a radio beacon system is developed hereinafter.

In the drawing- Figure l diagrammatically indicates a source of power I connected with a parallel connection to two loads 2 and 3 by means of passive networks 4 and 5.

Figure 2 diagrammatically illustrates one adaptation of my invention as applied to a twowire transmission line constituting either or both of the networks 4 and 5.

Figure 3 diagrammatically illustrates an adaptation of my invention including an artificial line section comprised of loading coils L and condensers C which may be used for either or both of the networks 4 and 5.

Figure 4 shows an adaptation of my invention applied to a source of power I series connected through a transformer T to loads 2 and 3 through passive networks 4 and 5.

Y Figure 5 diagrammatically illustrates the application of my invention to a directive antenna system, and,

Figure 6 shows the application of my invention to a radio range beacon station of the type disclosed in copending application Serial No. 669,539, filed May 5, 1933, by Harry Diamond.

In the circuit diagrammatically illustrated in Figure l, a sour-ce of power is designated as I, connected in parallel to loads 2 and 3 through passive networks 4 and 5, it being understood that additional loads may be connected to the source I through additional networks in a manner similar to those shown.

I have found that the transfer impedance of the network 5 may be expressed mathematically in which Z'rp. is the transfer impedance of the network 5, E1 is the voltage of the source I and I3 is the current flowing in the load 3. I have further found that if the constants of the network 5 are properly chosen it is possible to make the transfer impedance ZTR a function of the network 5 alone.

In the adaptation of my invention as illustrated in Figures 2 and 3 in which the network consists of a parallel wire transmission line or an artificial line, I have found that the transfer impedance may be represented by the following equation:

ZTR--Zo sinh 6+Z3 COSh 0 in which Zo is the surge impedance of the line either real or artificial, Z3 is the impedance of the load 3 and 6 is the complex phase angle of the transmission line or articial line. The value of 0 is determined as a function of the total attenuation of the system and the electrical length of the transmission line and is designated by the following equation:

0=otlB where a is the total attenuatio n B the electrical length of the line and y is \/-1.

If the hyperbolic cosine (cosh 0) of the complex phase angle 6 ofthe line is equa1 to zero,

then the transfer impedance may be represented by the following equation:

and the relation of the voltage of the source l (Ei) to the current in the load 3' (I3) is dependent entirely on the nature of the network 5. I have found that this relationship is accomplished when a approximates zero and the relationship of the system is represented by an equation.

cosh iBzcos B. This function is equal to zeroV when B is 90 or any uneven multiple of 90. In actual practice it is diicult to make the total attenuation of the system equal to zero, but it is relatively simple to obtainva value ofr a which is very small and closely approximating zero, so that to al1 intents and purposes for engineering practice this accuracy may be readily attained.

I have found that if the network 5 has negligible heat loss and has an electrical length of 90 and also that the surge impedance (Zo) of the line either real or artificial is equal to the desired ratio of E1 to I3, then the ratio of the voltage of the source l (E1) to the current in the load (Is) is determined and made independent of the nature of the impedance of the load 3 (Za) If the network 4 with its load 2 or any other additional circuit is likewise constructed in accordance with the foregoing principles, I have f found that theV current in the load 3 (I3) andA the current in the load 2 (I2) will be independent of the nature of the loads 2 and 3 inso far as their ratio to the voltage of the source (E1) is concernedV and will maintain a desired predetermined relationship to each other. The foregoing is applicable to the parallel connection of a source l to any number of loads (2, 3, connected by corresponding networks (4, 5 i

When it is desired to connect the loads in series and to energize the same from source I through networks l and 5, the following modifications must be made. As shown in Figure 4, the loads 2 and 3 are connected in series with each other and energized from the source l through the transformer T which comprises a primary winding A and two secondary windings B and C, which are so phased as to produce voltages in the directions indicated by the arrows in Fig. 4. In this arrangement the circulating current I is the same in each load with respect to both magnitude and phase of the current. If the loads 2 and 3 be separated by a considerable distance as is necessary in connection with directive antenna systems, I have found that it is possible by properly specifying the nature of the connecting networks to secure a constant relationship by determining the phase angle (0) of the line system or network such that the hyperbolic sine (sinh) thereof is approximately equal to zero (sinh ege); This requires that the heat loss in theconnected network be small and that B is 'equal' to any even multiple of 90. For such conditions then, ZTR=Z3- When the circuit has been arranged in this manner any change in the impedance of either of the loads 2 or 3 will change the current flowing through the network, equally affecting the current flowing in the other load in the same manner, both in phase and amplitude,l thereby automatically maintaining correct amplitude and phase between the currents flowing in the two'loads 2 and 3.

In other words, the networks, whether connected in series or parallel with the source, have lformer 'I' and passive networks i and 5.

the characteristic of ZTR=Z0 sinh 1-Z3 cosh 0. Sinh 0 approximates zero (0) and cosh 0 approximates one (1) when the networks are connected in series and with the source and when the networks are connected in parallel with the source sinh 6 rapproximates the square root of minus one (Vil) and cosh 6 approximates zero (0).

One embodiment of my invention is illustrated in Figure 5 in which is shown a transmission line antenna arrangement now used in the place of the loop antennas at radio range beacon stations.

The two vertical antennas designated 2 and 3 normally spaced 500 feet apart are supplied with current from the transmitter l through trans- If the characteristics of the networks il and 5 are determined in accordance with the foregoing principles, the currents in the antennas 2 and 3 are 1809 apart in phase and equal in magnitude. When two of the antenna systems shown in Figure 5 are placed atv right angles to each other, as shown in Figure 6 and described in co-pending` application Ser. No. 669,539, led May 5, 1933, by I-Iarry Diamond, the vertical antennas 2, 2

t and 3, 3 constitute the loads energized from a source of power I. The space pattern produced by the antenna system shown in Figure 5 is a gure of eight, which, when intersecting with the gure of eight radiated from the second antenna arrangement shown in Figure 6, produces four radio beacon courses. In order that these courses may be relied upon by aircraft, it is necessary that these courses remain xed. By the application of the foregoing principles of my invention to the networks 4, 4', 5, 5', by making the electrical length of the circuit from the transformer T to the coupling transformers C, T at the base ofeach antenna exactly 90 in length I have produced an antenna array in which the space pattern remains fixed, irrespective of changes in the weather conditions or alterationsI of conditions at any one of the several antennas.

While I have described my invention as applied particularly to directive antenna systems for radio beacon courses, it is to be clearly understood that the application thereof to other types of loads energized in series or in parallel from a common source come within the scope of my invention as dened in the claims appended hereto.

What I claim is:

l. In an electrical system, the combination of a source of alternating current, and a plurality of electrical loads energized from said source through passive networks each having the characteristic in which sinh 0 approximates the limits 0 and \/-1 and in which cosh 0 approximates the limits l and il, and in which ZTR is the transfer impedance of the passive networks, Z0 is the surge impedance of the passive network, Za is the impedance of the load, and 0 is the complex phase angle of the passive network.

2. I-n an electrical system, the combination of a source of alternating current, and a plurality of electrical loads energized from said source through passive networks each having the characteristic in which sinh 0 approximates 0, and in which ZTn 1s the transfer impedance of the passive networks, Zo 1s the surge impedance of the passive f network, Z3 is the impedance of the load, and a is the complex phase angle of the passive network.

3. In an electrical system, the combination of a source of alternating current, and a plurality of electrical loads energized from said source through passive networks each having the characteristic ZTR=Z sinh 6+Zs cosh 6 in which cosh 6 approximates 0, and in which ZTR is the transfer impedance of the passive network, Zu is the surge impedance of the passive network, Z3 is the impedance of the load, and 6 is the complex phase angle of the passive network.

4.` In a radio beacon system, the combination of a source of high frequency current, a plurality ofn antennas arranged about said source to form a space pattern and electrical networks coupling each antenna to said source each network having the characteristic in which sinh 6 approximates the limits 0 and V and in which cosh 6 approximates the limits 1 and 0, and in which ZTR is the transfer impedance of the passive network, Z0 is the surge impedance of the passive network, Z3 is the impedance of the load, and 6 is the complex phase angle of the passive network.

5. In a radio beacon system, the combination of a source of high frequency current, a plurality of antennas yarranged about said source to form a space pattern and electrical networks coupling each antenna to said source each network having the characteristic ZTR=Zo sinh 6+Z3 cosh 0 in which sinh 6 approximates 0, and in which ZTR is the transfer impedance of the passive network, Zo is the surge impedance of the passive network, Z3 is the impedance of the load, and 6 is the complex phase angle of the passive network.

6. In a radio beacon system, the combination of a source of high frequency current, a plurality of antennas arranged about said source to form a space pattern and electrical networks coupling each antenna to said source each network having the characteristic in which cosh 6 approximates 0, and in which ZTR is the transfer impedance of the passive network, Zo is the surge impedance of the passive network, Za is the impedance of the load, and

6 is the complex phase angle of the passive network.

7. An electrical system comprising a source of power and a plurality of loads of variable parameters, each of said loads being connected to said source by transmission lines including passive networks having the characteristic in which ZTR is the transfer impedance of the passive network, Z0 is the surge impedance of the line, either real or artificial, Z3 is the impedance of the load, and 6 is the complex phase angle of the transmission line or articial line, each of f said networks being so designed that sinh 6 approximates zero and cosh 6 approximates one.

8. An electrical system comprising a source of power and a plurality of loads of variable parameter, each of said loads being connected to said source through transmission lines including passive networks having the characteristic in which ZTR is the transfer impedance of the passive network, Zn is the surge impedance of the line, either real or artificial, Z3 is the impedance of the load, and 6 is the complex phase angle of the transmission line or artificial line, each of said networks being so designed that sinh 6 approximates VIT and cosh 6 approximates zero.

9. An electrical system comprising a source of power and a plurality of loads of variable parameters connected in series, each of said loads being connected to said source by a transmission aline, and means for maintaining constant phase and amplitude relations between the currents in said loads, said means comprising passive networks connected in each of said transmission lines and so designed as to make the electrical length of each of said transmission lines such that the currents in said loads will be dependent solely on the impedance of the loads.

l0. An electrical system comprising a source of power and a plurality of loads of variable parameters, each of said loads being connected to said source by a transmission line, and passive networks connected in each of said transmission lines, each of said passive networks being so designed as to make the electrical length of the transmission line in which it is connected such that the transfer impedance of each network will be equal to the impedance of the load connected thereto.

l1. An electrical system comprising a source of power and a plurality of loads of variable parameters, each of said loads being connected to said source by a transmission line, and means for maintaining constant phase and amplitude relations between the currents in said loads, said means comprising passive networks connected in each of said transmission lines and being so designed as to make the electrical length of each of said transmission lines such that the transfer impedance of each network will be equal to the surge impedance of the line.

l2. An electrical system comprising a source of power and a plurality of loads of variable parameters, each of said loads being connected in parallel to said source of power by a transmission line, and means for maintaining constant phase and amplitude relations between the currents in said loads, said means comprising passive networks connected in each of said transmission lines between each load and a source of power and having such characteristics and the constants thereof being so chosen as to make the electrical length of each of said transmission lines equal to or an uneven multiple thereof.

13. An electrical system comprising a source of power and a plurality of loads of variable parameters, said loads being connected in series and being connected to said source by transmission lines, and means for maintaining constant phase and amplitude relations between the currents in said loads, said means comprising passive networks connected in said transmission lines between each load and the source of power and having such characteristics and the constants thereof being so chosen as to make the electrical length of each of said transmission lines equal to an even multiple of 90.

FRANK G. KEAR. 

